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Wednesday, 6 February, 2002, 13:30 GMT
Spacecraft chases solar flares
Image of the Sun taken by the Soho spacecraft (Nasa)
Solar flares erupt near sunspots daily
The US space agency, Nasa, has launched a spacecraft that will study the most powerful explosions in the Solar System.

Solar flares happen 150 million kilometres (93 million miles) away from Earth but can damage satellites and interfere with terrestrial communications and power supplies.

The Hessi spacecraft (Nasa)
The mission will last for two years or more
The $85m mission was launched on Tuesday, nearly two years late.

The spacecraft, known as Hessi, the High Energy Solar Spectroscopic Imager, was released from a jetliner flying above the Atlantic Ocean off Florida.

Seconds later, a Pegasus rocket attached to the probe fired, sending Hessi into orbit above the Earth.

Mission controllers say the launch was successful and, if all goes to plan, solar images will be returned soon.

Launch delays

Scientists had wanted to launch the spacecraft last summer, when there was intense activity on the Sun.

Solar flares are the biggest explosions in the Solar System

Robert Lin, University of California at Berkeley
But the spacecraft was damaged during vibration tests in 2000 and rocket failures led to further delays.

Hessi will study X-rays and gamma rays emitted during flare-ups of the Sun. One solar flare can release as much energy as a billion megatons of TNT in a few minutes or less.

The solar flares can disrupt the upper atmosphere, leading to power and radio disruptions on Earth.

The project's chief scientist, Robert Lin, of the University of California at Berkeley, said: "Solar flares are the biggest explosions in the Solar System.

"They erupt near sunspots with the force of a hundred million hydrogen bombs."

See also:

23 Jan 02 | Sci/Tech
Here comes the Sun... again
14 Oct 01 | Sci/Tech
Spacecraft's solar polar pass
08 Aug 01 | Sci/Tech
'Sun catcher' finally flies
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